The present invention relates generally to information storage and retrieval systems and particularly to an apparatus thereof which may be employed to recover data from information tracks on an optical disc record.
A large-capacity data-storage system consists of a data base and a system for management and access of this data. In operation, users request stored data via a controller unit which is typically a data-management computer. Depending on the nature of a request, data is extracted from the mass memory and routed to the user.
Memories of currently existing systems are configured around magnetic storage media, and the variant forms of magnetic storage that conveniently accommodate the stored information. However, by the mid-1980s it is expected that the long-term or archival storage capacity and access rate capability of magnetic mass memories will be exceeded. Several goals have been established for possible systems: 3-second access time, potential library size of 10.sup.14 bits, long-term stability (10 to 15 years), high input/output rates (50 Mb/s), and bit error rate of about 10.sup.-10.
The requirement for 3-second access and 10-to-15 year archival quality represents major improvements over current magnetic-type systems. Access time, especially, is a major driving force in selection of the basic storage medium and in how stored data is accessed.
Of data formats in use today, the disk offers fastest access times to large amounts of stored data. Data is accessible in times typically on the order of tens of milliseconds to seconds, depending on the state of readiness of the disk when the information request is made. If the amount of information per disk can be substantially increased beyond the capacity of today's system, a disk-based mass memory becomes an attractive solution to the problems of achieving all of the desirable features listed above.
New technology presents several candidates for fast-access nonmagnetic mass memory disk storage media and systems. Generation of a system design involves selection of one of these media and solution of the electronic/mechanical handling and interfacing problems associated with the selected medium. Of the media candidates, it is believed that the optical disk is the most promising for archival digital data storage. Extrapolation from systems currently existing shows that the likelihood of successful application of the optical disk medium is high.
The information storage and retrieval system typically includes a storage module for storing a plurality of optical discs in protective cartridges in a particular arrangement. In order to access the cartridges, a disc changer has a carrier with at least two positioning and retracting carriers. These carriers have gripping means coupled to the carriers for gripping the cartridges. Each carrier has driving means to move the carrier and gripping means to the desired position. After the cartridge is gripped it is moved to an optical disc reader for reading data stored on the optical disc.
An example of an optical disc system is shown by U.S. Pat. No. 4,286,790, entitled, "Optical Disc Changer Apparatus," assigned to RCA, Inc. This apparatus stores the cartridges along a horizontal row and a changer moving in the "x" and "y" axes extracts the selected cartridge that is then positioned in a reader. The operation is reversed to store the cartridge.
The above system performs in the intended manner but involves time consuming movement along the horizontal row of cartridges.
The present invention is directed toward providing a carrousel type optical disc transport system that reduces linear movement to obtain a desired cartridge.